Decompression sickness (DCS) is a dangerous and occasionally lethal condition caused by nitrogen bubbles that form in the blood and other tissues of scuba divers who surface too quickly.

According to the Divers Alert Network, a worldwide organization devoted to safe-diving research and promotion, less than 1% of divers fall victim to DCS or the rarer bubble problem called gas embolism, air embolism, or arterial gas embolism. A study of the U.S. military community in Okinawa, where tens of thousands of sport and military dives are made each year, identified 84 DCS and 10 arterial gas embolism cases in 1989-95, including 9 deaths. This translated into one case in every 7,400 dives and one death in every 76,900 dives. But DCS symptoms can be quite mild, and many cases go unnoticed.

The air we breathe is mostly a mixture of two gases, nitrogen (78%) and oxygen (21%). Unlike oxygen, nitrogen is not converted...